Office tells you that Fred has it open and Fred swears to you that he doesn’t. Sometimes he is right, he has not got it open. There are two reasons for this

1) the Office apps read the hidden ~<filename.ext> and see who the owner is. Some times… (well lots of times really.”.) they are left behind , the next user opens the file and does not delete ~<filename.ext> , so the and word/excel still reads that !
2) For some reason the user is out of the document, but they need to log off their pc and log in again to close the file lock.

If you delete the ~<filename.ext> excel/word will tell you it is then open by “another user”, because it cannot read that hidden file and does not have the brains to read the owner of the ACTUAL file it is trying to open….

The only true way to tell who has the file open, is to right click on the file in windows explorer, select properties/security/advanced and see who the owner is. then you can yell at that user.